River blindness drug also kills mosquitoes

[DAKAR] A cheap, widely available drug commonly used to treat river blindness might reduce malaria transmission in Africa, according to research.

Researchers in Senegal and the United States found that the transmission of malaria dramatically fell over two weeks in Senegalese villages where people took the drug ivermectin — administered to kill the parasite responsible for river blindness, or onchocerciasis.

Nearly 80 per cent of mosquitoes died after feeding on the blood of villagers who had taken ivermectin. In villages where ivermectin was not taken, the mosquito population increased two and a half times over the same period.

"We conducted [our] study in the borough of Bandafassi, where the African Programme for Onchocerciasis Control conducts an annual campaign of mass distribution of ivermectin to fight river blindness," said Massamba Sylla, co-author of the study and an entomologist at Colorado State University, United States. "We took advantage of [this campaign] to verify and evaluate the effect of ivermectin on Anopheles gambiae mosquitoes."

Sylla, speaking to SciDev.Net in Senegal, said their work built on preliminary research conducted in 2006 and 2007.

The researchers collected mosquitoes from the villages, and verified in the lab that A. gambiae populations are sensitive to ivermectin at concentrations found in human blood. They found that mosquitoes died of paralysis up to four days after feeding on the blood of humans who had taken the drug.

"Ivermectin might have great importance as a tool for malaria control," said Sylla.

The researchers said the drug could be particularly useful during malaria epidemics or in well defined transmission seasons.

But larger, more detailed studies will be needed to verify the impacts on malaria transmission of more frequent ivermectin doses during the malaria season in Africa.

"This study offers good news on several fronts, not the least of which is the potential to disrupt the transmission of malaria and save needless suffering and death," said Peter J. Hotez, president of the American Society of Tropical Medicine and Hygiene. "We need more creative science like this that has simple yet powerful results in our battle against neglected diseases of poverty."

Colin Sutherland, reader in parasitology at the London School of Hygiene and Tropical Medicine, United Kingdom, thought the study was "an interesting piece of work".

"The true public health impact remains a little unclear at this stage, but we heartily welcome any news that a well-known and safe drug is reducing malaria transmission, under certain circumstances."

The study was published in the American Journal of Tropical Medicine and Hygiene last week (6 July).

Link to abstract in American Journal of Tropical Medicine and Hygiene